There is "good" which is a moral sense of the word and "good" which is virtuous. Which one do you mean?
Furthermore, Plato and Socrates are not Christian and did not believe in a God like Christians. They were not Christian.
Also, your question presupposes the existence ofd a god and implies that anyone who answers it must only choose one or the other of your suggestions.
In addition the questions suffers from an anachronistic error. You imply that the question Plato asks is in reference to a Christian god when in fact Christianity did not exist at the time this question was asked. As such, Plato did not and could not have meant what you mean.
It is also possible that neither notion of godness is correct and you do not take into consideration this possiblity. Moreover, anybody who happens to have a notion of goodness which is not based on a montheistic notion of god is left out.
So to answer your question, I would say that the questions begs of itself and is riddled with fallacious reasoning. Therefore the question can not be answered because it is illogical.
The definition of the word "goodness" does not boil down to one of your choices. It can be something else and most certainly has been considered as such historically.
Lastly, atheists, agnostics, any religious person who does not believe in "one" god can not answer your question. This implies that these people can't think properly.